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authorHuang Ying <ying.huang@intel.com>2009-06-15 15:37:07 +0800
committerH. Peter Anvin <hpa@zytor.com>2009-06-16 16:56:04 -0700
commit184e1fdfea066ab8f12a1e8912f402d2d6556d11 (patch)
treef9ffff79d1924f530e582a2aab9f0cb032f0a4e3 /arch
parent300df7dc89cc276377fc020704e34875d5c473b6 (diff)
x86, mce: fix a race condition about mce_callin and no_way_out
If one CPU has no_way_out == 1, all other CPUs should have no_way_out == 1. But despite global_nwo is read after mce_callin, global_nwo is updated after mce_callin too. So it is possible that some CPU read global_nwo before some other CPU update global_nwo, so that no_way_out == 1 for some CPU, while no_way_out == 0 for some other CPU. This patch fixes this race condition via moving mce_callin updating after global_nwo updating, with a smp_wmb in between. A smp_rmb is added between their reading too. Signed-off-by: Huang Ying <ying.huang@intel.com> Acked-by: Andi Kleen <ak@linux.intel.com> Acked-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/cpu/mcheck/mce.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index fabba15e4558..19294b8524cb 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -703,6 +703,11 @@ static int mce_start(int no_way_out, int *order)
}
atomic_add(no_way_out, &global_nwo);
+ /*
+ * global_nwo should be updated before mce_callin
+ */
+ smp_wmb();
+ *order = atomic_add_return(1, &mce_callin);
/*
* Wait for everyone.
@@ -717,6 +722,10 @@ static int mce_start(int no_way_out, int *order)
}
/*
+ * mce_callin should be read before global_nwo
+ */
+ smp_rmb();
+ /*
* Cache the global no_way_out state.
*/
nwo = atomic_read(&global_nwo);
@@ -862,7 +871,7 @@ void do_machine_check(struct pt_regs *regs, long error_code)
* Establish sequential order between the CPUs entering the machine
* check handler.
*/
- int order;
+ int order = -1;
/*
* If no_way_out gets set, there is no safe way to recover from this
@@ -887,7 +896,6 @@ void do_machine_check(struct pt_regs *regs, long error_code)
if (!banks)
goto out;
- order = atomic_add_return(1, &mce_callin);
mce_setup(&m);
m.mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS);